Magnetic position sensor on a common supporting element

ABSTRACT

The invention relates to a magnetic position sensor in the case of which at least two stator elements are arranged in a magnetic field and a magnetic field probe is located in the measuring air gap between the stator elements, a means tracking a moving object being arranged parallel to the plane defined by the stator elements.  
     A magnetic position sensor which can be produced simply and cost-effectively has a stator element and a magnetic field probe which are arranged on a common supporting element.

[0001] The invention relates to a magnetic position sensor in the case of which at least two stator elements are arranged in a magnetic field and a magnetic field probe is located in the measuring air gap between the stator elements, a means tracking a moving object being arranged parallel to the plane defined by the stator elements.

[0002] Hall angle sensors are known which output signals which are proportional to angles. The detection of a rotary movement is performed in this case via a Hall probe which is located in an air gap which is constructed between two stator halves.

[0003] A rotor is fixedly arranged on a shaft which, in turn, is connected to the object whose change in position is to be detected.

[0004] The stator elements are fastened to the sensor housing. The Hall sensor is arranged in the measuring air gap between the stator elements in a radial fashion relative to the direction of rotation of the shaft, with the result that its electric terminals project beyond the stator elements and are connected to an evaluation circuit on a printed circuit board in order to produce the electric connection.

[0005] Disadvantageous in this case is the complicated mounting of the sensor, since it is necessary for the mounting of the stator elements, on the one hand, and the electric connection between the Hall probe and the printed circuit board, on the other hand, to be performed in separate method steps.

[0006] It is therefore the object of the invention to specify a magnetic position sensor which can be produced simply and cost-effectively.

[0007] According to the invention, the object is achieved by virtue of the fact that at least one stator element and the magnetic field probe are arranged on a common supporting element.

[0008] Particularly when the supporting element is aligned parallel to the radial extent of the stator element, it is possible to reduce the size of the design of the magnetic position sensor and to mount stator elements and the magnetic field probe, in common with other electronic components, on the supporting element in a single method step.

[0009] The stator element advantageously has a region, angled off in the direction of the supporting element, for fastening the stator element to the supporting element. The end of said angled-off region can be placed during mounting directly onto the copper cladding of the printed circuit board and be butt-fastened, for example by reflow soldering.

[0010] In a further embodiment, adjoining the first angled-off region of the stator element is a second angled-off region which is constructed parallel to the supporting element and is connected thereto. In this variant, the second angled-off region is connected in a planar fashion to the copper cladding of the supporting element, and this permits a better adhesion of the stator to the supporting element. This part, as well, can be fastened simply to the supporting element by means of surface soldering.

[0011] In a particularly simple embodiment, the stator element is constructed as a bent stamping which presses directly on the supporting element. The stator element thus constructed has at least one offset which is inserted into the supporting element through an opening therein and fixed there on the opposite side.

[0012] The production as a bent stamping permits rivets and washers to be dispensed with, with the result that the mounting process can be automated by means of soldering. The possibilities of configuring the stator elements can also be combined.

[0013] In one embodiment, the magnetic field probe is arranged radially offset relative to a shaft in the measuring air gap, the shaft being fixedly connected to the rotor, which is arranged in the axial direction relative to the stator elements.

[0014] The rotor is constructed in two parts, each soft-magnetic rotor element having at least one circular segment and the rotor elements being interconnected rigidly rotated with respect to one another, with the result that the circular segment of the first rotor element is situated opposite a segment gap in the second rotor element, the stator elements being arranged between the rotor elements, and a magnet which generates the magnetic field in the axial direction being arranged both between the rotor elements and the stator elements.

[0015] The advantage of the invention consists in that the rigid bipartite rotor configuration suppresses the effects of the axial play on the sensor signal, since the two air gaps occurring between the rotor and stator are simultaneously varied in opposite directions and the sum of the air gaps is therefore always constant.

[0016] The sum of the two air gaps, which are constructed in the axial direction between the rotor elements and one stator element each, is preferably small compared to the axial extent of the magnet, as a result of which the magnetic flux through the stator is supported.

[0017] In one embodiment, the stator elements are likewise constructed to resemble circular segments.

[0018] In one development, the outside radius of the circular segment of at least one rotor element is smaller than the outside radius of a stator element. This permits the arrangement of the magnetic field probe parallel to the axis of rotation of the shaft of the sensor in the air gap between the two stator elements. The advantage of this arrangement consists in that the magnet can now be optimally dimensioned, since the axial spacing between the two rotor parts can be varied freely.

[0019] Since the angular dependence of the flux guidance is achieved not via the contour or magnetization of the magnet, but by the asymmetric shape of the rotor, the requirements placed on the magnet are minimal.

[0020] The magnet need only generate an axially directed field. The latter can be generated optionally by a rotatably mounted permanent magnet or a magnet which is fixed with reference to the stator and which in this case can be embodied either as a permanent magnet or as an electromagnet.

[0021] In one development, the magnet is constructed as a permanently magnetic annular magnet.

[0022] The stator segments are advantageously arranged in this case always coaxially around the axis of rotation of the rotor shaft.

[0023] The invention permits numerous exemplary embodiments: one of them is to be explained in more detail with the aid of the figures represented in the drawing, in which:

[0024]FIG. 1 shows a pedal unit of a motor vehicle,

[0025]FIG. 2 shows a section through a magnetic position sensor which is arranged on the pedal unit of the motor vehicle,

[0026]FIG. 3 shows a representation of the principle of the magnetic position sensor,

[0027]FIG. 4 shows an arrangement of the stator element of the magnetic position sensor on a printed circuit board,

[0028]FIG. 5 shows a stator element, and

[0029]FIG. 6 shows possibilities for fastening the stator elements on the printed circuit board.

[0030] Identical features are marked in the figures with identical reference numerals.

[0031] In accordance with FIG. 1, an acceleration pedal 1, for example a gas pedal of a motor vehicle, is connected in a secure fashion in terms of rotation to the shaft 2 which, for its part, is rotatably mounted in the bearing block 3. The restoring spring 6 is supported, on the one hand, on a lug 4, constructed in one piece with the acceleration pedal 1, and, on the other hand, on a lever 5 which can be rotated about a shaft 8 and bears frictionally with its other end against a rotating surface 9 of the acceleration pedal 1. The result is to form a frictional resistance (hysteresis) opposing the pivoting movement of the acceleration pedal 1 in both directions, unintentional vibrations of the acceleration pedal 1 thereby being largely suppressed.

[0032] The action of the restoring spring 6 is limited by an inner stop 7, on which the lug 4 comes to bear when the acceleration pedal 1 is not being operated.

[0033]FIG. 2 represents the arrangement of an angle sensor on the bearing block 3 of the acceleration pedal 1. The housing 10 of the angle sensor is connected to the bearing block 3 via a screw connection 12 (merely indicated).

[0034] The housing 10 has a plug-in connection 13, which permits electric connection to the printed circuit board 14, which is arranged inside the housing 10 on the projections 16 of the housing 10.

[0035] The shaft 2, guided out of the bearing block 3 through an opening 11, accommodates a non-magnetic shaft 15 which is constructed in stages. 2 rotor elements 17 a and 17 b are arranged securely in terms of rotation on said shaft 15, for example constructed as a plastics shaft, in such a way that they enclose axially an annular magnet 19 and two stator elements 18 a and 18 b. The stator elements 18 a and 18 b are arranged on the printed circuit board 14. The rotor element 17 b is movably guided through an opening 20 in the printed circuit board 14. The side of the plastics shaft 15 averted from the shaft 2 is guided movably in a receptacle 21 of the housing 10.

[0036] The housing 10 is constructed in one piece with the plug receptacle 13 and the receptacle 21.

[0037] The principle of the sensor is represented in FIG. 3 and is to be explained below.

[0038] The magnet 19 is located between rotor elements 17 a, 17 b which are made from soft magnetic material which are rotated by 180° with respect to one another. The rotor elements 17 a and 17 b are rigidly coupled to one another via the plastics shaft 15.

[0039] In the simplest case, each rotor element has two segments 17 a 1, 17 a 2 or 17 b 1 and 17 b 2, which are arranged opposite one another. The first rotor element 17 a has segments 17 a 1, 17 a 2 which are displaced by 180° with respect to one another, while the second rotor element 17 b likewise has two segments 17 b 1, 17 b 2. The rotor elements are magnetically coupled in the direction of the center of rotation. The two rotor elements 17 a, 17 b are offset with respect to one another such that a segment gap of the rotor element 17 b is situated opposite the segment 17 a 1 of the rotor element 17 a. The same holds for the segments 17 b 1, 17 b 2 of the second rotor element 17 b, which are always situated opposite a segment gap of the first rotor element 17 a. In this arrangement, it is in each case the spacing between two segments 17 a 1, 17 a 2 or 17 b 1, 17 b 2 of a rotor element 17 a or 17 b, respectively, which are denoted as a segment gap.

[0040] However, it is conceivable that the rotor elements 17 a, 17 b have N segments. The rotor elements are then offset by 180°/N with respect to one another. As already explained, the width of each wing in this case is correspondingly 180°/N. The periodicity of the signal with respect to the semicircular variant is thereby reduced by 1/N.

[0041] The system represented in FIG. 3 has a stator arrangement which comprises two segments 18 a 1, 18 a 2 arranged directly juxtaposed. The stator segments 18 a 1 and 18 a 2 are arranged between the rotor elements 17 a, 17 b and form with respect to one another an air gap 23 in which the Hall probe 22 is arranged axially relative to the shaft 15.

[0042]FIG. 3 shows a redundant system in which, in addition to the stator segments 18 a 1 and 18 a 2 already explained, a second pair of stator segments 18 b 1, 18 b 2 is also constructed, which is arranged rotated by 180° with respect to the first pair of stator segments 18 a 1, 18 a 2. The stator segments 18 b 1 and 18 b 2 also form a measuring air gap 23, in which a second magnetic field probe 22 is arranged.

[0043] In this embodiment, the stator segments 18 a 1, 18 a 2, 18 b 1 and 18 b 2 are provided with a larger outside radius R2 than the rotor segments 17 a 1, 17 a 2 and 17 b 1, 17 b 2. The rotor segments have an outside radius R1 which is dimensioned such that the Hall elements 22 can be introduced completely into the measuring air gap without having the rotor segment 17 a 1, 17 a 2 or 17 b 1, 17 b 2 superimposed on them.

[0044] The Hall probes 22 arranged axially relative to the direction of rotation of the sensor in the measuring air gap 23 can now be arranged on one and the same printed circuit board 14.

[0045] The magnet 19 can be optimally dimensioned, since the axial spacing between the two rotor elements 17 a, 17 b can be freely selected.

[0046] A simplification in mounting the sensor as a whole is achieved when the circular segment of the first rotor element has a smaller angle than the segment gap of the second rotor element.

[0047]FIG. 3 represents an example in which the segmentation into 57° has been undertaken and a redundant signal is generated.

[0048] Open regions of 66° here, for example, are produced between these two stator pairs 18 a 1, 18 a 2; 18 b 1, 18 b 2.

[0049] The rotor element 17 a has two segments 17 a 1, 17 a 2 of single stator width (57°). The rotor element 17 b is of complementary construction, that is to say the gaps have an extent which corresponds to the width of the circular segments 17 a 1, 17 a 2 of the rotor element 17 a.

[0050] If the rotor packet 17 a, 17 b is brought into a suitable position which corresponds to ±90° relative to the position represented, said packet can be assembled or dismantled as a whole axially.

[0051] It is possible thereby to achieve a substantial simplification in mounting, since the stator side (printed circuit board 14) with stators and electronics can be handled, just like the rotor side (rotor elements 17 a, 17 b, magnet 19 and shaft 15) as preassembled units.

[0052] For example, the rotor side can be preassembled on the non-magnetic shaft 15, which is then pressed onto the shaft 2. The plastics element permits magnetic decoupling of the shaft 5, which can then consist of a soft magnetic material. The shaft also no longer needs to be offset, and this likewise signifies a simplification.

[0053]FIG. 4 represents an embodiment of the sensor just described in which the stator elements 18 a 1 and 18 a 2 as well as 18 b 1 and 18 b 2 rest directly on the printed circuit board 14.

[0054] The stator elements 18 a 1 and 18 a 2 as well as 18 b 1 and 18 b 2 are constructed as bent stampings. Each stator element has an angled-off part 24 or 25, respectively, in each case on its outer segment edges 29 (FIG. 5). Together with the angled-off part 25 of the stator segment 18 b 1, the angled-off part 24 of the stator segment 18 b 2 forms the measuring air gap 23 in which the magnetic field probe 22 is arranged.

[0055] These angled-off parts enlarge the effective measuring surface without the need for the sheet thickness of the stator to be increased. The result of this is that the dimensioning of the magnet 19 can be reduced, the entire sensor thereby having smaller dimensions.

[0056] The electric terminals 28 of the Hall sensor 22 engage in the printed circuit board 14 and are flow-soldered on the underside of the printed circuit board 14.

[0057] A stator segment is represented once again in FIG. 5. It is represented on the example of the segment 18 a 1 that there are arranged on the edge having the largest outside radius R2 two offsets 26, 27 which engage in openings in the printed circuit board 14. The segments 18 a 1, 18 a 2, 18 b 1, 18 b 2 are fastened with the aid of said offset 26, 27 to the printed circuit board 14 by being flow-soldered in one operation simultaneously with Hall sensors 22 and further electric switching elements (not further represented) arranged on the printed circuit board 14.

[0058] Yet further possibilities of fastening the stator segments are represented in FIG. 6. FIG. 6.1 shows a stator element 18 a 1, which has a prescribed spacing from the printed circuit board 14. A region 30, angled off perpendicular, of the stator segment 18 a 1, or a region 31 of the stator segment 18 a 2 is placed in abutment on the copper cladding 32 of the printed circuit board 14 and connected to the latter by reflow soldering. The angled-off region 30, 31 serves in this case simultaneously as a spacer between the stator segment 18 a 1 and the printed circuit board 14.

[0059] In the variant represented in FIG. 6.2, the first 90° angled-off part 30 of the stator element 18 a 1 is adjoined by a second region 33 angled off by 90°, which is constructed parallel to the printed circuit board and rests on the latter in a planar fashion and is soldered. The stator element 18 a 1 forms a U rotated by 90° with the two angled-off regions 30 and 33.

[0060] Both in the variant in accordance with FIG. 6.1 and in the embodiment according to FIG. 6.2, the first angled-off parts 30 of each stator segment form with the first angled-off part 31 of the stator segment adjoining parallel thereto the measuring air gap 23 in which the Hall probe 22 is arranged. 

1. A magnetic position sensor in the case of which at least two stator elements are arranged in a magnetic field and a magnetic field probe is located in the measuring air gap between the stator elements, a means tracking a moving object being arranged parallel to the plane defined by the stator elements, wherein at least one stator element (18 a, 18 b) and the magnetic field probe (19) are arranged on a common supporting element (14).
 2. The magnetic position sensor as claimed in claim 1, wherein the supporting element (14) is aligned parallel to the radial extent of the stator elements (18 a, 18 b).
 3. The magnetic position sensor as claimed in claim 2, wherein the stator element (18 a, 18 b) has a region (30, 31), angled off in the direction of the supporting element (14), for fastening the stator element (18 a, 18 b) to the supporting element (14).
 4. The magnetic position sensor as claimed in claim 3, wherein the angled-off region (30, 31) is butt-soldered on the supporting element (14).
 5. The magnetic position sensor as claimed in claim 4, wherein adjoining the first angled-off region (30, 31) of the stator element (18 a, 18 b) is a second angled-off region (33, 34) which is constructed parallel to the supporting element (14) and is connected thereto.
 6. The magnetic position sensor as claimed in claim 3, wherein at least one offset (26, 27) of the stator element (18 a, 18 b) is inserted in openings in the supporting element (14) and soldered there.
 7. The magnetic position sensor as claimed in one of the preceding claims, wherein the stator element (18 a, 18 b) is a bent stamping which rests directly on the supporting element (14).
 8. The magnetic position sensor as claimed in claim 2 or 7, wherein the stator elements (18 a, 18 b) have at least one angled-off part (24, 25), the measuring air gap (23) accommodating the magnetic field probe (22) being constructed between the angled-off parts (24, 25) of two juxtaposed stator elements (18 a, 18 b).
 9. The magnetic position sensor as claimed in claims 1 and 8, wherein the magnetic field probe (22) is arranged parallel to a shaft (15) in the measuring air gap (23), the shaft (15) being connected to a rotor (17 a, 17 b) which axially encloses the stator elements (18 a, 18 b).
 10. The magnetic position sensor as claimed in claim 9, wherein the rotor is constructed in two parts, each soft-magnetic rotor element (17 a, 17 b) having at least one circular segment (17 a 1, 17 a 2, 17 b 1, 17 b 2) and the rotor elements (17 a, 17 b) being interconnected rigidly rotated with respect to one another, with the result that the circular segment (17 a 1, 17 a 2) of the first rotor element (17 a) is situated opposite a segment gap in the second rotor element (17 b), the stator elements (18 a, 18 b) being arranged between the rotor elements (17 a, 17 b), and a magnet (19) which generates the magnetic field in the axial direction being arranged both between the rotor elements (17 a, 17 b) and the stator elements (18 a, 18 b).
 11. The magnetic position sensor as claimed in claim 10, wherein the sum of the two air gaps, which are constructed in the axial direction between the rotor elements (17 a, 17 b) and one stator element (18 a, 18 b) each, is small compared to the axial extent of the magnet (19).
 12. The magnetic position sensor as claimed in claim 10, wherein the stator elements (18 a, 18 b) are constructed to resemble circular segments.
 13. The magnetic position sensor as claimed in claims 10 and 12, wherein the outside radius (R1) of the circular segment (17 a 1, 17 a 2, 17 b 1, 17 b 2) of at least one rotor element (17 a, 17 b) is smaller than the outside radius (R2) of a stator element (18 a, 18 b).
 14. The magnetic position sensor as claimed in one of the preceding claims, wherein the magnet (19) is constructed as a permanently magnetic annular magnet.
 15. The magnetic position sensor as claimed in claim 15, wherein the annular magnet (19) is fastened to the rotor shaft (15).
 16. The magnetic position sensor as claimed in one of claims 10 to 14, wherein the stator elements (18 a, 18 b) are arranged coaxially around the axis of rotation of the rotor shaft (15).
 17. The magnetic position sensor as claimed in claim 1, wherein the rotor comprising the rotor elements (17 a, 17 b) and the rotor shaft (15) can be assembled or dismantled as a whole axially. 